1. Field of the Invention
The present invention relates to hand operated bicycle gear transmission device, and more particularly, to a multi-stage gear transmission device for bicycle comprising manual operation part, handle bar fixing function part, steel transmission cable guide part and gear position fixing part with which to carry out effective and reliable power transmission and speed change for a bicycle.
2. Description of the Prior Art
Generally, a well known conventional bicycle with multi-stage gear transmission device transmits power by appropriate combination of gear set in the gear transmission device according to different road condition.
Especially for long distance excursion in a bad road course, it is important for a bicycle to have a reliable and stable gear transmission in addition to an exact gear shift effect for speed change. The gear transmission system for speed change in a bicycle usually comprises a large chain wheel, a chain, both for power transmission, a rear sprocket wheel, a gear transmission device, a gear shift lever. According to operation manner of the gear shift lever, the gear shift lever can be classified a single gear shift lever, a dual returnable gear shift lever and a hand operated gear shift lever which is resembling the present invention. Among the above three types, the single gear shift lever is simplest in construction and easiest for manufacture and assembly. However, it has the disadvantages of too large operation range and uncomfortableness caused by stiff contact feeling of the lever end to the rider""s palm. In addition, the positioning of this type is carried out by frictional force, which in certain cases, for example, riding on a severely vibrating rugged road, may cause lost of engaging force of the shift lever. As a result, the chain fails to be settled at its exact gear position.
As for the dual returnable gear shift lever, although it can considerably attain a precise positioning effect even in a bad riding environment, yet the operation and positioning effect have to be performed with the cooperation of two sets of mechanism. As a result, the constitution of the gear shift lever mechanism becomes complicated which leads to increase of production and assembly costs. Therefore, it is mostly adopted by high class bicycles.
In order to eliminate the shortcomings inherent to the conventional technique as mentioned above, the inventor of the present invention has made hard study and trials in this field persistently for a long time, and finally has succeeded in disclosing the present invention.
It is an object of the present invention to provide hand operated bicycle gear transmission device having steel transmission cable guide part and gear position fixing part independently carrying out their respective functions for the convenience of assembly and maintenance.
It is another object of the present invention to provide hand operated bicycle gear transmission device which can be simply operated to perform speed change of a bicycle.
It is still another object of the present invention to provide hand operated bicycle gear transmission device of a simple construction so as to facilitate assembly and repair work.
To achieve these and other objects, gist of the present invention is directed to provide hand operated bicycle gear transmission device comprising a handle bar fixing base, a cover fixing base, a rubber cover, a positioning plate, positioning protuberances, saucer shaped aprings, a circular fixing hole for the steel cable head, a steel cable guide groove and a stroke compensating means. Incidentally, hand operated bicycle gear transmission device of the present invention utilizes cooperative function of a plurality of positioning recessed slots formed around the rigid positioning plate, the positioning protuberances provided at the rear of the cover fixing base and the saucer shaped springs adjacent to the positioning plate to provide mutual engagement force therebetween so as to achieve an excellent positioning effect of gear transmission even under the worst riding environment. As a result, the hand operated bicycle gear transmission device of the present invention has lots of merits such as being conveniently operatable with a small applied force to perform speed change smoothly, having simplified and easy looking construction with small amount of components, and being able to be easily assembled and repaired.